1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device having a semiconductor element with at least one connection region, in which the contact resistance of the at least one connection region is reduced and in which unfavourable influences of doping elements are avoided.
2. Description of the Related Technology
Due to an increase in integration of devices which comprise, for example, MOSFETs (metal oxide semiconductor field-effect transistors) and are fabricated with the aid of MOS or CMOS processes, the miniaturization of these devices represents an ongoing challenge. Not only do the dimensions and regions of the device need to be reduced in size, but also there continue to be high expectations with regard to quality and yield. The requirements imposed on the junctions in devices of this type are related to a very high activation of the doping, good control of the depth of the junction, etc. At the same time, contacts with a low resistance via silicides are required in order to allow contact via the back surface.
A method for fabricating an IGFET which includes a gate electrode with a low resistance is known from U.S. Pat. No. 5,851,891, which describes the fabrication of an IGFET (insulated gate field-effect transistor) in which the gate electrode of the IGFET is made from silicon and a connection region is formed therein by enabling the silicon to react with a metal applied to it so as to form a metal silicide. Apart from in the vicinity of the dielectric region, the silicon of the gate electrode is doped with doping atoms, such as boron atoms. When the metal silicide is being formed, these doping atoms are forced towards the dielectric region without penetrating through it. On the other hand, the relatively high doping concentration formed in this way in the vicinity of the dielectric region ensures that an undesirable depletion layer effect does not occur in the gate electrode, since such an effect would increase the effective thickness of the dielectric region. The expulsion of doping atoms before the interface of the silicide which is formed is known as the snowplough effect.
One drawback of the method described above is that there is nevertheless still a risk of doping atoms penetrating into or through the dielectric region, which is unfavourable for the electrical properties of the semiconductor element.